The Robert C. Martin Clean Code Collection (Collection) (Robert C. Martin Series)

by Robert C. Martin

The problem with this statement is that it is hard to know what “one thing” is. Does Listing 3-3 do one thing? It’s easy to make the case that it’s doing three things: 1. Determining whether the page is a test page. 2. If so, including setups and teardowns. 3. Rendering the page in HTML. So which is it? Is the function doing one thing or three things? Notice that the three steps of the function are one level of abstraction below the stated name of the function. We can describe the function by describing it as a brief TO4 paragraph: TO RenderPageWithSetupsAndTeardowns, we check to see whether the page is a test page and if so, we include the setups and teardowns. In either case we render the page in HTML. If a function does only those steps that are one level below the stated name of the function, then the function is doing one thing. After all, the reason we write functions is to decompose a larger concept (in other words, the name of the function) into a set of steps at the next level of abstraction.